Superfluidity in fermionic systems originates from pairing of fermions, and Bose condensation of these Cooper pairs. The Cooper pairs are usually made of fermions of different species; thus the most favorable situation for pairing and superfluidity is when the two species of fermions that form pairs have the same density. This paper studies the possible superfluid states when the two pairing species have different densities, and show that the resultant states have remarkable similarities to the phases of liquid crystals. This enables us to provide a unified description of the possible pairing phases and understand the phase transitions among them.
Possible quantum liquid crystal phases of helium monolayers
